Layered preform

ABSTRACT

A preform for use in the production of a container in a blow-molding operation includes an inner parison molded in a first mold to include a finish portion including a mouth-defining opening, a threaded outer surface adapted to engage a container closure, and a lower margin including a support ring, a closed bottom portion including a gate vestige, and a barrel portion extending between the finish portion lower margin and the bottom portion, and an outer parison molded in a second mold and consisting essentially of a barrel portion having a length similar to the inner parison barrel portion and a bottom portion including an opening for receiving the inner parison gate vestige, the outer parison having an inner surface conformably matching the inner parison outer surface. The outer parison is mechanically telescopically assembled over the inner parison outside the first and second molds to form a layered preform, the preform optionally including an intermediate layer. The layered preform can also include a handle including a ring portion having an inner diameter similar to the inner parison barrel portion outer diameter, and a gripping portion projecting outward from the ring portion, the handle ring portion being positioned between the outer parison barrel portion and the inner parison finish portion.

BACKGROUND OF THE INVENTION

The present invention relates generally to preforms for use in blowmolding containers formed of polymeric resins. The inventionparticularly relates to such preforms having more than one layer ofresin.

Preforms having more than one layer of resin material have been used inblow molding operations to form containers having multi-layered walls.The layered preforms can be formed by co-extrusion or co-injection ofmultiple polymer streams of resin into a single mold. Such co-injectionprocesses are sometimes difficult to control and are subject to layerthickness variation as a result of variations in control parameters. Aseries of injection processes has also been employed to form a layeredpreform in a series of molds, the preform being transferred from mold tomold in the process of adding each new layer. The thickness build up ofthe preform using such a process translates into longer cooling timessince cooling of the newly injected layer of plastic can only beachieved through contact of one side of the layer of resin. Any of theseprocesses can be used to form a layered preform in which recycled resinforms an outside layer of the preform while virgin resin forms an insidelayer of the preform, the inside layer forming the portion of thecontainer most likely to experience contact with foods, beverages,drugs, cosmetics or the like within the container. For the purposes ofthis invention, all resin not suitable for food contact under part 177of title 21 of the United States Code of Federal Regulations isconsidered as the equivalent to recycled resin.

It has also been suggested to independently mold two or more layers inseparate molds and to thereafter form a preform by assembling a seriesof layers together. This method has the advantages of direct control ofeach layer of thickness since it is formed in a separate moldspecifically fashioned for that layer where thickness tolerances can becarefully controlled. The process is also advantageous in that eachlayer is very thin and subject to cooling from both sides and thereforethe production of each layer can be comparatively rapid. Since thelayers can be simultaneously formed in separate molds, this formationtime, even when added to the assembly time, can yield faster productionfor a preform over that experienced for molding a single or multiplelayer preform in a single fixed mold. However, the subsequent handlingof such an assembled preform has, on occasion, proved difficult as theassembled layers of the preform have a tendency to de-laminate,partially or entirely, prior to the blowing operation.

SUMMARY OF THE INVENTION

In accordance with the present invention, a layered preform for use inthe production of a plastic container in a blow molding operationcomprises an inner parison molded in a first mold to include a finishportion having a lower margin, a closed bottom portion, and a barrelportion extending between the finish portion and the bottom portion. Anouter parison is molded in a second mold and consists essentially of abarrel portion having a length similar to the inner parison barrelportion and a bottom portion including an opening. The outer parison ismolded to have an inner surface which conforms generally to the shape ofthe inner parison outer surface. The outer parison is mechanicallyassembled over the inner parison outside the first and second molds andretaining means are provided for retaining the parisons in fixedposition relative to each other to form the layered preform.

The retaining means can be formed at the juncture of the lower margin ofthe finish portion of the inner parison and the upper margin of theouter parison by thermally welding the two margins together throughlocal induction heatings laser heatings or spin-welding. In anotherembodiment, the closed bottom portion of the inner parison includes agate vestige while the opening in the outer parison bottom portion isspecifically sized to receive the gate vestige on the inner parison, theretaining means comprising a thermally welded portion of the gatevestige to the margin of the outer parison bottom opening.

Once the retaining means is formed thus assuring no movement between theinner and outer parisons, the layered preform can be heated toblow-molding temperature. For polyethylene terephthalate and many otherresins, the blow-molding temperature is sufficiently near the glasstransition temperature that the confronting surfaces of the two layersbecome tacky and, if made of a sufficiently common resin material,adhere to one another.

In another embodiment, the layered preform further comprises a handleformed in a separate mold to include a ring portion having an innerdiameter similar to the inner parison barrel portion outer diameter. Agripping portion of the handle projects outward from the ring portion.The ring portion is positioned between the outer parison barrel portionand the inner parison finish portion. In the subsequent heating of thelayered preform prior to blow-molding, care must be taken to prevent thegripping portion of the handle from deforming unacceptably. In thesubsequent blow-molding operation, the handle can be positioned inpockets provided in the parting plane of the blow mold.

In still another embodiment, the layered parison further comprises atleast one additional layer of material sandwiched between the innerparison and the outer parison. The at least one additional layer ofmaterial preferably contributes additional properties to the containerand can comprise a gas barrier layer consisting essentially of a resinmaterial having a gas permeability less than either resin forming theinner parison or the outer parison. The suitability of the resinmaterial forming the additional layer or layers depends on theproperties of the resins selected to form the inner and outer parisonsand desired performance criteria generally known in the art, forexample, as disclosed in U.S. Pat. Nos. 4,482,586; 4,501,781; 4,574,148;4,919,984; 4,959,421; and 5,077,111.

Other features of the present invention and their inherent advantageswill become apparent to those skilled in the art upon considering thefollowing description of preferred embodiments which refers to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a mold in which an inner parison,according to the present invention, is molded.

FIG. 2 is a sectional view of a mold in which an outer parison,according to the present invention, is molded.

FIG. 3 is a sectional view showing the mechanically assembly of an innerand outer parison according to the present invention.

FIG. 4 is a sectional view of a layered preform constructed from theassembly shown in FIG. 3.

FIG. 5 is a sectional view of a layered preform in accordance with thepresent invention including a handle.

FIG. 6 is a sectional view of a layered preform in accordance with thepresent invention including an additional layer of material sandwichedbetween the inner and outer parisons.

The thickness of the materials forming each layer of the layered preformhave been exaggerated in the figures for clarity.

DESCRIPTION OF THE PREFERRED EMBODIMENT

A mold 10 for forming an inner parison 12 in accordance with the presentinvention is shown to include a core member 14, a cavity member 16 and athread split 18. The core member 14, cavity member 16 and thread split18 are shown together in the closed position suitable to receive moltenplastic under pressure from injection head 20 through gate 22 into thecavity forming the parison 12. Various cooling channels 24 includingfountain 26 within the core 14 are provided for cooling the plasticforming parison 12. The inner parison 12 is shown to include a finishportion 28 including support ring 30 formed between the thread split 18and the core 14. The inner parison 12 also includes a closed bottomportion 32, a gate vestige 34 extending downwardly from the closedbottom portion 32 and a barrel portion 36 extending between the bottomportion 32 and a lower margin of the finish portion 28. The closedbottom portion 32 and barrel portion 36 of inner parison 12 are formedbetween the core 14 and the cavity 16. The gate vestige 34 is formedbetween the bottom portion 32 of parison 12 and gate 22 within cavity16.

A second mold 38, shown in FIG. 2, is used to form an outer parison 40according to the present invention. The mold 38 includes a core 42 whichcooperates with cavity 44 to define the space into which molten plasticis injected from injection head 46 through a specially configured ringgate 48 into the space between the core 42 and cavity 44. Again, coolingchannels 50, including fountain 52, are provided for cooling the plasticto form the outer parison 40. The outer parison 40 is shown to have abarrel portion 54 and a bottom portion 56, the bottom portion 56including a central opening 58 defined by the ring gate 48.

After the inner parison 12 and the outer parison 40 have been molded inmolds 10 and 38, respectively, they are removed from the molds andtelescopically assembled as shown in FIG. 3 by coaxially moving theinner parison 12 and outer parison 40 in the direction of arrows A andB, respectively, until the upper margin 64 of parison 40 contacts thelower margin 66 of parison 12. The hole 58 in the bottom of outerparison 40 permits air to exit from the space 60 between the twoparisons as they are telescopically assembled. The hole 58 in the bottomof outer parison is sized to receive the gate vestige 34 protrudingdownward from the bottom 32 of inner parison 12.

Upon completion of the coaxial movement of the inner parison 12 andouter parison 40, the two parisons form a layered preform 62 as shown inFIG. 4. Once assembled, the inner parison 12 and outer parison 40 areretained together in fixed position relative to each other by aretaining means which can take several forms.

In a first form of the retaining means, the inner parison 12 and outerparison 40 are rotated quickly with respect to each other for a timesufficient to spin-weld the upper margin 64 of the barrel portion 54 ofouter parison 40 to the lower margin 66 of the support ring 30. Thespin-weld formed retaining means of the layered preform is situated in aregion where, upon subsequent blowing of the preform in a blow mold, theregion undergoes negligible expansion. A similar retaining means can beformed at the same location by localized induction heating of themargins 64 and 66, by laser welding of one or more points of the margins64 and 66, or by other methods apparent to those skilled in the art.

An alternative retaining means can be formed by thermally welding aprotruding portion 68 of the gate vestige 34 to the hole 58 at thebottom of the outer parison 40. The thermal weld can be formed by directcontact of the protruding portion 68 with a source of heat sufficient toplastically deform the protruding portion outwardly to extend overand/or bond with a lower margin of hole 58. The means for forming thethermal weld at the bottom of the outer parison 40 can include laserspot welding, and other methods apparent to those skilled in the art.

In yet another embodiment of the retaining means, the outer parison 40is assembled onto the inner parison 20 under conditions wherein theouter parison is significantly hotter than the inner parison and whereinthe inside diameter of the outer parison 40 is dimensioned relative tothe outside diameter of inner parison 12 such that through thermalcontraction upon arriving at the same temperature no dimensionaldifference exists between the two parisons thereby insuring significantfrictional engagement over the entire length of the mating surfaces ofthe barrel portions of the two parisons. When this thermal contractionretaining means is employed, special care may have to be employed in thereheating of the layered perform prior to blowing the container toinsure uniform heating of both the inner and outer parisonsimultaneously so that no dimensional differences arise which wouldreduce the frictional engagement between the two parisons until bothparisons are sufficiently near the glass transition temperature that theconfronting surfaces adhere to one another.

Another layered preform 70, according to the present invention, is shownin FIG. 5 to comprise an inner parison 12 substantially as previouslydescribed in the preceding figures. The layered preform 70 furthercomprises an outer parison 72 similar to parison 40 of the previousfigures, but with a barrel portion 74 slightly shorter in length thanbarrel portion 54 of outer parison 40. A ring-shaped member 76 issituated between the lower margin 66 of parison 12 and an upper margin78 of outer parison 72. An inner surface 80 of the ring member 76contacts the outer surface of barrel portion 36 of inner parison 12. Ahandle 82 or other similar appendage protrudes radially outward from thering member 76 to provide for easy handling of the container to beformed from the preform 70. The ring member 76 is situated in thelocation shown in FIG. 5 by assembling the ring member 76 onto the innerparison 12 prior to or during the assembly of the outer parison 72 ontothe inner parison 12 in a manner similar to that shown in FIG. 3. Theretaining means retaining the inner and outer parisons in fixed positionrelative to each other also retains the ring member 76 and integralappendage 82 at the desired location. In the subsequent heating of thelayered preform prior to blow-molding it into a container, care must betaken to prevent the gripping portion of the handle 82 from deformingunacceptably. In the subsequent blow-molding operation, the handle 82 ispreferably positioned in pockets provided in the parting plane of theblow mold. The shape of the handle 82 is variable depending on thenature and function of the container to be formed from the layer preform70, the variation in shape being generally apparent to those skilled inthe art of plastic bottle making.

Layered preform 84, shown in FIG. 6, is yet another embodiment of thepresent invention. The preform 84 is formed from an inner parison 12, aspreviously described, an outer parison 86 having an inner diameter of atleast the length of the barrel portion 88 which is slightly larger thanthe outer diameter of the barrel portion 36 of inner parison 12 therebydefining a space 90 for receiving at least one additional layer ofmaterial 92 which is sandwiched between the inner parison 12 and theouter parison 86. As illustrated, the inner surface of the outer parison86 includes a step 94 at the lower margin of the region defining space90. Below the step 94, the outer surface of the bottom portion 32 ofinner parison 12 and the inner surface of bottom portion 96 of outerparison 86 are in physical contact. Preferably the position of the lowerstep 94 is designed such that when the layered preform 84 issubsequently blow molded into a container, the additional layer ofmaterial 92 is situated in the side wall of the container while thebottom portions 32 and 96 of the parisons are situated in the bottom ofthe container. The additional layer of material 92 can be formed byextruding a tubular sleeve of coating material, and slipping the sleeveof coating material over the barrel portion 36 of the inner parison 12prior to the mechanical assembling of the inner and outer parisons 12and 86.

This feature is particularly advantageous when the at least oneadditional layer of material 90 is a gas barrier layer formed of a resinhaving a gas permeability less than either of the resins forming theinner and outer parisons 12 and 86, respectively, since the predominantlocation for gas migration is through the side wall of a blow moldedcontainer while only a small portion of gas migrates through the bottomof the container which is generally physically thicker. The preferredresin material for forming a gas barrier layer is a mixture of a verysmall proportion of a resin having low oxygen permeability such as nylonwith a large proportion of a resin matching the chemistry of the innerand outer parisons.

Although the invention has been described in detail with reference tocertain illustrated preferred embodiments, variations and applicationsexist within the scope and spirit of the invention as described in thefollowing claims.

What is claimed:
 1. A layered polymeric resin preform for use in theproduction of a plastic container in a blow-molding operation, thepreform comprising:an inner parison molded in a first mold to include afinish portion having a lower margin, a closed bottom portion, and abarrel portion having an outer surface extending between the finishportion lower margin and the bottom portion, the inner parison closedbottom portion including a gate vestige, an outer parison molded in asecond mold and consisting essentially of a barrel portion including aninner surface having a length about equal to the inner parison barrelportion outer surface and a bottom portion including an opening, theouter parison being mechanically assembled over the inner parisonoutside the first and second molds so that the outer parison innersurface fully contacts the inner parison outer surface, and retainingmeans for retaining the parisons in fixed position relative to eachother to form a layered preform, the opening in the outer parison bottomportion being sized to receive the gate vestige of the inner parison,whereby the parisons are held in fixed position relative to each otherin subsequent heating and blow molding of the container, and a handleincluding a ring portion having an inner diameter about equal to theinner parison barrel portion outer diameter, and a gripping portionprojecting outward from the ring portion, the ring portion beingpositioned between the outer parison barrel portion and the innerparison finish portion.
 2. A layered polymeric resin preform accordingto claim 1 wherein said retaining means comprises a thermally weldedportion of the gate vestige to the margin of the outer parison bottomopening.
 3. A layered polymeric resin preform according to claim 1wherein the inner parison consists essentially of virgin polymericmaterial and the outer parison consists essentially of recycledpolymeric material.
 4. A layered polymeric resin preform according toclaim 1 wherein the outer parison comprises at least two layers of resinmaterial.
 5. A layered polymeric resin preform for use in the productionof a plastic container in a blow-molding operation, the preformcomprising:an inner parison molded in a first mold to include a finishportion having a lower margin, a closed bottom portion, and a barrelportion having an outer surface extending between the finish portionlower margin and the bottom portion, the inner parison closed bottomportion including a gate vestige, an outer parison molded in a secondmold and consisting essentially of a barrel portion including an innersurface having a length about equal to the inner parison barrel portionouter surface and a bottom portion including an opening, at least oneadditional layer of material sandwiched between the inner parison andthe outer parison, the outer parison being mechanically assembled overthe inner parison outside the first and second molds so that theadditional layer of material fully contacts the outer parison innersurface and the inner parison outer surface, and retaining means forretaining the parisons in fixed position relative to each other to forma layered preform, the opening in the outer parison bottom portion beingsized to receive the gate vestige of the inner parison, whereby theparisons are held in fixed position relative to each other in subsequentheating and blow molding of the container, and a handle including a ringportion having an inner diameter about equal to the inner parison barrelportion outer diameter, and a gripping portion projecting outward fromthe ring portion, the ring portion being positioned between the outerparison barrel portion and the inner parison finish portion.
 6. Alayered polymeric resin preform according to claim 5 wherein said atleast one additional layer of material is a gas barrier layer consistingessentially of a resin material having a gas permeability less than thegas permeability of either resin forming the inner and outer parisons.7. A layered polymeric resin preform for use in the production of aplastic container in a blow-molding operation, the preform comprising:aninner parison molded in a first mold to include a finish portion havinga lower margin, a closed bottom portion including a gate vestige, and abarrel portion including an outer surface extending between the finishportion lower margin and the bottom portion, an outer parison molded ina second mold and consisting essentially of a barrel portion includingan inner surface having a length about the same as the inner parisonbarrel portion outer surface and a bottom portion including an openingsized to receive the gate vestige of the inner parison, the outerparison being mechanically assembled over the inner parison outside thefirst and second molds so that the outer parison inner surface conformsto the inner parison outer surface, a portion of the gate vestige beingreceived in and welded to the margin of the outer parison bottom openingfor retaining the parisons in fixed position relative to each other toform a layered polymeric resin preform, and a handle including a ringportion having an inner diameter about equal to the inner parison barrelportion outer diameter, and a gripping portion projecting outward fromthe ring portion, the ring portion being positioned between the outerparison barrel portion and the inner parison finish portion.
 8. Alayered polymeric resin preform according to claim 7 further comprisingat least one additional layer of material, sandwiched between the innerparison and the outer parison, consisting essentially of a resinmaterial having a gas permeability less than the gas permeability ofeither resin forming the inner and outer parisons.
 9. A layeredpolymeric resin preform according to claim 7 wherein the inner parisonconsists essentially of virgin polymeric material and the outer parisonconsists essentially of recycled polymeric material.
 10. A layeredpolymeric resin preform according to claim 7 wherein the outer parisoncomprises at least two layers of resin material.
 11. A layered polymericresin preform for use in the production of a plastic container in ablow-molding operation, the preform comprising:an inner parison moldedin a first mold to include a finish portion having a lower margin, aclosed bottom portion including a gate vestige, and a barrel portionincluding an outer surface extending between the finish portion lowermargin and the bottom portion, a handle including a ring portion havingan inner diameter equal to the inner parison barrel portion outerdiameter, and a gripping portion projecting outward from the ringportion, the ring portion being positioned coaxially over the innerparison barrel portion and contiguous to a lower margin of the innerparison finish portion, and an outer parison molded in a second mold andconsisting essentially of a barrel portion having an inner surfaceincluding an upper margin, the outer parison barrel portion having alength less than the inner parison barrel portion and a bottom portionincluding an opening sized to receive the gate vestige of the innerparison, the outer parison being mechanically assembled over the innerparison outside the first and second molds so that the upper margin ofthe outer parison barrel portion is contiguous to a lower margin of thehandle ring portion and the outer parison inner surface conforms to theinner parison outer surface, a portion of the gate vestige beingreceived in and welded to the margin of the outer parison bottom openingfor retaining the parisons in fixed position relative to each other toform a layered polymeric resin preform.